It is well known that golf shafts are asymmetric with respect to the force required to bend the shaft in different directions to a given flex point. This asymmetry, referred to as a neutral flex point, spine line or weld line, typically occurs as a result of the manufacture of the shaft. When golf clubs are manufactured the asymmetry is often ignored resulting in a set of golf clubs which, by visual inspection, are matched yet the flex of sister clubs may vary due to the different rotation of the flex assymetry relative to the neutral position of the golf head.
It has long been the desire to mitigate the differences by aligning the neutral flex point in a consistent orientation relative to the club head. For example, Colbert in U.S. Pat. No. 4,958,834 describes the desire to align the shaft seam with the club face in a consistent manner yet the manner in which this is done is not set forth except as a visual technique.
Karner, et al., U.S. Pat. No. 5,771,552 teaches the alignment of a golf shaft with a squared club for aesthetics. The device of Karner, et al., has several deficiencies. First, the club face may be concave or convex which would provide a faulty alignment of the club relative to the shaft alignment window. For example, if the club face is concave, a club head which is slightly forward (towards the toe) may be oriented with the toe behind the heel in a configuration typically resulting in a slice. This is acceptable for aesthetics but could be unacceptable if accuracy in aligning flex properties were desired.
Ciccarello et al., U.S. Pat. No. 5,976,028, describes a method for determining the neutral flex point, or shaft seam. There is no indication in Ciccarello et al. how a skilled artisan could align a shaft properly with the golf head. To date the alignment has been done by visual inspection.
It has long been felt in the industry that the effect of proper use of the shaft assymetry could enhance the performance of a golf club. While this has been the opinion it has not yet been fully tested since the methods for accurately orienting the shaft assymetry has been lacking. For example, alignment of the shaft asymmetry with a device such as Karner et al. would provide some information yet the ability to accurately deviate from the square position to test for regions of improved properties is lacking. There is no technique for aligning a shaft neutral flex point at a non-neutral optimal position, for example +15° from neutral, except for visual estimation which is unacceptable. Furthermore, even if improved properties are realized from the studies which are only now made available with the present invention there is no manner in which the improvement could be utilized since there is no method for accurately orienting the club face and the shaft assymetry prior to the present invention.
Yet another problem in the art is the inability to determine the relationship between the shaft asymmetry and golf head in a prepared club. Prior to preparation, the shaft assymetry can be located as described in the cited art. After the club head is secured to the shaft there is no way of determining, without disassembly, if the golf shaft is aligned in any specific orientation.
There has been a long felt desire in the art for a method of accurately aligning a golf club head with a shaft neutral flex point repeatedly. There has also been a desire to determine, after assembly, the alignment of the shaft neutral flex point with the golf head.